IMessage is Apple's proprietary instant messaging services for iOS and Mac OS. Users have outlined their issues
in several Apple support forum
discussions (here and here),
where they complain about being unable to send or receive messages. The problems appear to affect users across the globe, suggesting that the problem
is on Apple's end as opposed to that of a service provider.

Apple introduced iMessage as part of iOS 5 last October, offering users on the iPhone, iPod, and iPad a way to communicate with one another for free as long as they had an Internet connection. Apple added the functionality to its Macs as part of Mountain Lion in July.

The reported iMessage problems follow an outage at Apple's iCloud service a few days ago, in which millions of users were unable to access e-mail for a couple of days. Apple said little about that problem except that it was working on it and would have it corrected ASAP. ICloud e-mail is now operational.

Apple's iCloud status page currently states that "all services are online." This status page, however, has been unreliable, or at least slow to update, where outage are concerned.

A poll on tech site 9to5mac shows that about half of users are experiencing problems with the service and cannot reliably send or receive messages.